基于广义力的旋翼振动载荷计算

为描述挥舞、摆振铰和变距轴承的运动引入了三个刚体运动自由度 ,旋翼桨叶通过 5节点15自由度有限单元离散 ,计入了桨叶刚性运动与非线性弹性变形之间的动力学耦合效应。利用曲线坐标系下的本构方程 ,对经典的中等变形梁理论进行了重新的推导。另外 ,采用了Leishman Beddoes非定常和动态失速模型 ,入流由自由尾迹分析获得。导出的旋翼桨叶非线性时变常微分方程以广义力的形式给出。桨叶截面载荷和运动方程在位形空间中同时求解。由本文分析得出的桨叶振动载荷与SA349/ 2小羚羊直升机飞行测试数据吻合程度很好。

Rotor Vibratory Load Prediction Based on Generalized Forces

Three rigid-body-motion DOFs are introduced for the motion of the flap, lag hinge and pitch bearing. The rotor blade is discretized using a five-nodes, 15 DOFs beam finite element. The dynamic coupling effect between the rigid motion of the blade and the nonlinear elastic deflections is taken into account. Utilizing the constitutive law of the curvilinear coordinate system, the typical moderate deflection beam theory is reformulated. In addition, the Leishman and Beddoes unsteady and dynamic stall model is incorporated and the inflow is evaluated with the free wake analysis. The derived nonlinear ordinary differential equations with time-dependent coefficients of the rotor blade are given in the sense of the generalized forces. The sectional loads of the blade and the equations of motion are solved simultaneously in the physical space. The blade vibratory loads predicted by present analysis show generally fair agreement with the flight test data of the SA349/2 Gazelle helicopter.